CD-ROM CACHING, Q: What benefits would caching CD-ROM drives bring us?

Most disk cache software including DOS' and Windows' SMARTDRV
cache hard disks but cannot cache CD-ROM drives.  A cache
would speed up reading CD-ROM data.  When data is first
requested from the CD-ROM disc, the cache picks up more data
from the CD-ROM disc than is currently being requested, with
the expectation that further requests will follow.  Another
request occurs and data is retrieved more rapidly if the data
requested is in the cache residing in memory.  Only a few
disk cache software can cache CD-ROM drives; these include
Norton Speedcache+, OPTI-CDcache, Lightning CD, and CD
Speedway.

How much a performance improvement can be expected?
Opinions vary but it is clear that software caches are not a
universal panacea and that performance improvement is best
sought first with the new generation of multispin or double-
speed CD-ROM drives.  My tests with Norton Speedcache+ using
1-2 megabyte caches, a Hitachi CDR-1700s CD-ROM player running
SilverPlatter's text-based Aquatic Sciences and Fisheries
Abstracts CD-ROM on two microcomputers (25 MHz 486 & 16 MHz
386) show a 9-16% frequency in getting data from the cache
rather than from the CD-ROM disc.  This 9-16% improvement is
much less than the improvement seen with Speedcache+-based
hard disk caching on the same microcomputers.  This 9-16%
improvement in performance was not readily discernible
onscreen with the text-based SilverPlatter Aquatic Sciences
and Fisheries Abstracts CD-ROM.  Keyword searching was not
faster and scrolling down through retrieved text appeared
only marginally better.  It would probably take a larger
performance increase to be dramatically visible.

Taschek stated that text-based CD-ROM tasks improved
dramatically with Speedcache+ or Lightning CD.  Chernicoff
stated that performance with Speedcache+, and an NEC
Multispin CD-ROM drive and a Trantor SCSI controller, was
"visibly quicker" with text-based CD-ROMs and that a larger
cache improved performance, particularly with contiguous data
on CD-ROM.  Tittell determined that CD Speedway improved
performance 10-20 times.  Vaughan-Nichols found that
SpeedCache+ increased throughput performance by 10% for a
600-millisecond access-time Sony CD-ROM drive, and, that
Speedcache+ did not appreciably improve the performance of
multimedia applications.

Though CD-ROM disc caching does deliver performance
improvement, it appears that the degree of improvement will
be variable depending on a variety of factors.  Money is best
spent on getting a higher performance CD-ROM drive with CD-
ROM disc caching software relegated to a secondary purchase
consideration.

Chernicoff, David P.  "SpeedCache Plus 4.0".  PC Week 10(18):
105, May 10, 1993.

Grimes, Brad.  Online's products boost the performance of CD-
ROM drive.  PC Magazine 12(10): 64, May 25, 1993.

Taschek, John.  "Attention CD-ROM owners: make your drive run 28 times faster"
PC-Computing 6(7):66, July 1993.

Tittel, Ed. "CD-Speedway 1.20b".  Windows User 2(7):72,
August 1993.

Vaughan-Nichols, Steven J.  "Break the disk speed limit with
SpeedCache+".  Computer Shopper 12(12):726, December 1992.



PRODUCTS MENTIONED

CD Speedway, $99
BLOC Publishing Corp.
800 SW 37th Ave, Suite 765
Coral Gables, FL 33134, 305/445-0903

Lightning CD, $99.95
Lucid Corp.
101 W. Renner Rd., Suite 450
Richardson, TX 75082-2017, 800/925-8243, 214/994-8100

Opti-CDcache, $89.
Online Computer Systems Inc.,
20251 Century Blvd.,
Germantown, MD 20874, 800/922-9204, 301/428-3700

Speedcache+, $99
Symantec Corp.
10201 Torre Ave.
Cupertino, CA 95014-2132, 800/441-7234, 408/252-3570